Does cardiac resynchronisation therapy improve survival and quality of life in patients with end-stage heart failure?

Abstract

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether bi-ventricular pacing, also referred to as cardiac resynchronisation therapy (CRT), improves survival and quality of life in patients with severe (NYHA III/IV) symptomatic heart failure. Cardiac pacing can be achieved by stimulation of the right ventricle, left ventricle (LV) or by bi-ventricular pacing. This best evidence topic considers only bi-ventricular pacing. This involves placement of pacing leads in the right ventricle, epicardially on the LV with a lead typically placed in a branch of the coronary sinus and, unless the patient is in permanent atrial fibrillation, in the right atrium. Bi-ventricular pacing allows the optimisation of atrio-ventricular timing and resynchronisation of septal and postero-lateral left ventricular contraction. Symptomatic heart failure has a high morbidity and a poor prognosis. Patients with dyspnoea at rest or on minimal exertion (NYHA III/IV) are at high risk of death due to progressive heart failure, while those with less severe symptoms are more likely to experience sudden cardiac death. Up to 50% of patients with NYHA class III/IV symptoms have a prolonged QRS duration (>120 ms) on 12-lead ECG (usually in a LBBB pattern). This intra-ventricular conduction delay is a surrogate marker of mechanical dyssynchrony (an uncoordinated regional contraction-relaxation pattern) and is associated with reduced cardiac output and increased mortality. Bi-ventricular pacing can reduce the delay in activation of the LV free wall found in many patients with LV systolic dysfunction, thereby improving mechanical synchrony and cardiac output. It may also reduce pre-systolic mitral regurgitation. Three hundred and fifty-six papers were identified using the search method outlined, nine randomised controlled trials and a meta-analysis in addition to published guidelines presented the best evidence to answer the clinical question. Current best available evidence suggests that in patients with left ventricular systolic dysfunction (LVEF </=35%), prolonged QRS duration (QRS >or=120 ms), and NYHA class III or IV symptoms despite optimal pharmacological therapy, bi-ventricular pacing significantly reduces the number of hospitalisations from heart failure, improves functional status (NYHA class, peak oxygen uptake and exercise tolerance) and improves health related quality of life. The CARE-HF study also demonstrated a reduction in mortality from progressive heart failure and all-cause mortality.